Oil well treatment

ABSTRACT

Chemical additives are forced into wells using the pressure above atmospheric pressure, at which the well&#39;&#39;s product issues from the well. The additive is forced into the casing of the well and product from the inner tubing string is used to flush the additive down. Apparatus for practicing that method includes a pump connected to pump the additive from a supply container into the well casing. The motor or prime mover for the pump is driven by the pressurized product of the well whereby no external power source is required. The pump delivers additive at higher pressure than the pressure at which product drives the pump motor but it delivers a smaller volume of additive than the volume of product that drives the motor. The structure includes a timing device which results in operation of the pump through a number of cycles at each well treatment and spacing of treatments as desired. It provides for flushing with product during the course of each treatment.

[451 Aug. 26, 1975 United States Patent 11 1 tal.

iguiane 3,212,406 10/1965 McDuffic............................417/403 [51' OIL WELL TREATMENT lnventors: Thaddeus M. Doniguian, 913

Emerald Bay, Laguna Beach, 92651; Jared Erle Larsen, 16440 Mount ArartSt.; Susumu Assistant ExaminerJack E. Ebel Takabayashi, 9076 ColumbineAve., both of Fountain Valley, Calif. 92708 Attorney, Agent, orFirm-Grover A. Frater [57] ABSTRACT Chemical additives are forced intowells using the 22, Filed: Aug. 13, 1973 Appl 387,890 pressure aboveatmospheric pressure, at which the wells product issues from the well.The additive is forced into the casing of the Well and product from theinner tubing string is used to flush the additive down. Apparatus forpracticing that method includes a [52] US. 166/64; 166/75; 166/244 C;

E21B 33/03 pump connected to pump the additive from a supply containerinto the well casing. The motor or prime mover for the pump is driven bythe pressurized prod- [58] Field of Search............ 91/165; 166/53,64, 75,

511, 513 uct of the well whereby no external power source is required.The pump delivers additive at higher presl References C'ted sure thanthe pressure at which product drives the UNITED STATES PATENTS pumpmotor but it delivers a smaller volume of additive than the volume ofproduct that drives the motor. The structure includes a timing devicewhich results in operation of the pump through a number of cycles ateach well treatment and spacing of treatments as desired. It providesfor flushing with product during the course of each treatment.

1 Claim, 4 Drawing Figures 35475245 W HW MW M6B66 /66 76266766 4 .AL 4 mmm H W m m 2 mm mm m mmp uc mm m n m h n mflfl m m w m mm m .1 .1 maivml h SRCMSBWT 009592355 23456666 99999990 HHHHHHHH 6049630 56370005543367-3007 .2 .3 2. 737434 560000597 b 24 b3333 sol "44 2.50

PATENTED AUB26 I975 CLOCK OSCILLATOR on. WELL TREATMENT This inventionrelates to improvements in methods and means for transferring quantitiesof chemical into oil wells and other kinds of wells.

The invention is particularly useful for introducing corrosioninhibiting chemicals into the casing of wells of the kinds that employan outer casing which houses a tubing string through which the wellsproduct flows at positive pressure. The preferred embodiment includesthe step of, and the means for, employing the wells product (oil andwater or water alone) in flushing the chemical additive down into thecasing. In some instances other fluids are available for flushing andthe use of such fluids is also envisioned within the invention.

Not only is the oil well an important application for the invention, itis often a difficult application and for that reason the embodimentselected for illustration in the drawings is one intended for treatingoil wells. The quantity of corrosion inhibitor that is added to a welland the frequency of that treatment in an optimum treatment programvaries greatly from well to well, and for a given well, can vary greatlyfrom time to time. In some cases the well is treated only once a week.In other cases it may be desirable to treat the well every several daysor every day. In the past, a service man equipped with a service truckvisited each well periodically. The casing was opened and a quantity ofchemical was added. That chemical was usually flushed down the casingusing water or a petroleum product from a flushing liquid containercarried on the truck.

A preferred arrangement would be' to leave a supply of chemical at thewell together with an automatic ap paratus for injecting that chemicalperiodically. Doing that is relatively simple if an electric power lineor other adequate supply of power is available. However, many wells arenot located near a power line and in those cases the well treater hascontinued to make his rounds. The product of most wells issues from thewell at positive pressure so that power source is available at the well.However, that pressure is often not very great. In many cases the casingitself is pressurized and on occasion its pressure may actually exceedthe pressure at which the product is delivered. That circumstanceprevents effective and reliable use of the pressure differences betweenwell tubing and well casing to force the additive into the well casing.In the invention some of the product is released to do the work ofpumping chemical into the casing. The product is made to operate a primemover which is coupled to a pump. The pump and the prime mover arearranged so that there is a multiplication of mechanical force fromprime mover to pump whereby chemical is forced into the well casing at apressure exceeding the pressure of the product. The price paid for thatincreased pressure is reduced volumetric capacity. To overcome thatdifficulty the invention provides an apparatus which recycles until therequisite amount of chemical has been supplied to the well casing.

To provide such a solution to the problem and such an apparatus areobjects of the invention. Another object is to provide an apparatuswhich is so dependable and so reliable that it will operate to injectchemical into a well periodically over a period of many monthsautomatically and without the need of visitation by an attendant. Arelated object is to provide that result notwithstanding that thepressure of the product may vary during that time and notwithstandingthat the pressure difference between well casing and well tubing maychange and may even be reversed at times.

Since chemical is added periodically, some means must be provided in theinvention for keeping track of time. Power to operate the timer may bederived from the wells pressurized product or, because the amount ofpower required is very small, it can be conveniently supplied by a smallinexpensive battery capable of operating a timer for many months.

It is desirable to flush the chemical additive down the well ifpossible. Since the product is ordinarily pressurized above the casingpressure it is feasible to use the wells product as the flushing fluidand the preferred form of the invention includes utilization of thepressure differential between the tubing and atmosphere to divert" someof the product back down into the casing. That product may be a gas, oroil, or water, or a combination of them.

One of the objects of the invention is to provide an apparatus that iseasily and reliably installed. The preferred embodiment includes a primemover and pump arrangement that is adapted for use with a conventional55 gallon steel drum. A drum full of chemical is delivered'to the wellsite where the prime mover and pump are installed in the bung hole atthe top of the drum. The pump can also be installed in the bung hole atthe side of a horizontally positioned drum. One advantage of theinvention resides in the fact that the drum can be refilled whereby theapparatus need not be moved or disturbed to replenish the supply.

These and other objects and advantages of the invention will be apparentfrom an examination of the drawings in which:

FIG. 1 is a schematic diagram of the apparatus of the inventionassociated with an oil well head;

FIG. 2 is a view partly in elevation and partly in section of thecontrol structure and pump and prime mover mechanism employed in theapparatus in FIG. 1;

FIG. 3 is a schematic diagram of the control valve employed in theapparatus of FIG. 2; and

FIG. 4 is a block diagram of the timing circuitry and is an oil well.Its tubing string 12 is contained in the easing 14. The product of theoil well is a mixture of gas,

'oil and water. It is delivered to the fitting 16 where it istransferred to a line 18 which leads to a storage facility not shown. Athree-way valve 20, which may comprise two two-way valves, is includedin that line. The valve is normally positioned so that the product flowsthrough the valve to the gas separator-accumulator 22. Gas accumulatesin the upper portion of the unit 22. It is used to operate the gas motor24 that operates threeway valve 20, or to operate gas motor 25 thatoperates two-way valves 27 and 28. A manually operated threeway valve 21applies the gas to a selected one or the other of motors 24 and 25.Ordinarily only one of those motors is used. The valve 21, one of themotors 24 or 25 and the valve it operates would be omitted. The gas alsois used to power the controller and pump and prime mover unit 26. Gasfrom the separatoraccumulator 22 flows through a filter 29 and line 30to unit 26 where a control valve 44 controls its application to line 32and motor 24 or motor 25. That same control valve applies gas to theprime mover of a pump. The latter pumps chemical down from drum 34 to aline 36 from which it flows into flushing line 38. Line 38 extends fromthe normally closed outlet of three-way valve 20, and from the normallyclosed outlet of twoway valve 28, to the interior of casing 14. Whenpressure is applied to line 32, the motor 24 operates to divert productfrom line 18 to line 38 to flush the chemical additive from that lineand down the casing. On the other hand if the three-way valve 21 isadjusted so that the flow of gas is from line 32 to motor 25 rather thanmotor 25, valve 27 will be closed and valve 28 will open to permit aflow of flushing water from the lower outlet of the separator to theflushing line 38. Other flushing fluid is sometimes available and mightbe used instead.

In this embodiment a small quantity of chemical is pumped into line 38during a few seconds of successive l to 2-minute intervals. During theinterval the valve is operated, or valves 27 and 28 are operated, todivert product to the flushing task. The number of cycles is selected sothat some predetermined quantity of chemical is added. In one practicalembodiment the pump cycles five times and delivers just over a pint ofchemical to the well. This alternate pumping and flushing in cycles ispreferred. It permits injection of chemical at relatively high pressureand it interrupts the steady state pressure relationships in the systemfor only short periods.

The pump and pump motor, or prime mover, are shown in FIG. 2 in apreferred form suitable for use with steel drums of the kind that have abung hole opening at their upper ends or at their sides. Cylinder 40 andpiston 42 are part of the driver. When pressurized gas entering controlvalve 44 by line 30 is permitted to flow by line 50 to the space abovepiston 42, the piston is forced downwardly toward shoulder 48.Subsequently, valve 44 diverts the pressurized product gas from line 50to lines 46 and 32. Line 46 communicates with the lower end of cylinder40 where the gas -it brings to the cylinder forces the piston back up.

The valve 44 is shown schematically in FIG. 3. Ports 52 and 54 areexhaust ports. Line 30 connects to inlet port 56. The two cylinder ports58 and 60 connect to lines 46 and 50, respectively. Two spools 62 and 64are carried on an operating shaft 66 which is biased by spring 68 to theupper position shown in FIG. 3. In that position spool 62 closes exhaustport 52 and opens port 58 to permit flow of gas from inlet port 56. Gascannot flow from the inlet port 56 to the other cylinder port 60.Instead, port 60 is vented through exhaust port 54. When valve stem 66is up, piston 42 is up or is going up. When the valve stem 66 isdepressed, port 58 is opened to exhaust port 52. Exhaust port 54 isclosed by spool 64 and cylinder port 60 is connected to inlet port 56.In this valve position, drive piston 42 is down or is going down.

Since line 32 is pressurized whenever line 46 is pressurized, the motor24 and valve 20 are operated, or the motor and valves 27 and 28 areoperated, and flushing fluid flows when piston 42 is up or is going up.

The piston 42 is carried on an axle shaft. The shaft 70 extendsdownwardly from the piston, through shoulder 48 into the second pumpcylinder 72. The shoulder 48 is formed as part of the upper end of acylindrical coupler 74. An O-ring fitted into a groove in the wall ofthe shaft opening cooperates with the shaft to seal the volume belowpiston 42 from the volume above piston 84.

The upper end of the lower cylinder is fitted and sealed withincylindrical coupler 74. The upper outer end of the coupler is fitted andsealed into the inner lower end of cylinder 40. The lower end ofcylinder 4 is threaded to fit the bung hole threads of the drum 34. Whenthe unit is to be assembled on the drum, the bung closure is removed andthe cylinder 40 is screwed in'Lo the opening.

Air is admitted into the drum to equalize pressure as chemical isremoved. Air enters through the annealed space between cylindricalcoupler 74 and cylinder 40 below line 36.

The lower interior of cylindrical coupler 74- has reduced diameter toform an inside shoulder 82. The shoulder limits upward movement of thepump piston 84. A cup seal 86, carried by piston 84, prevents flowaround the piston. But flow is permitted through piston 84 on its downstroke by way of passages 88 which extend through its opening. At thebottom inside of the piston 84, an annular valve seat is formed by an inwardly and upwardly extending, conical wall 90. The head 92 for thatseat is carried at the end of shaft 70. The lower portion of the shafthas reduced diameter to form a shoulder 94. The pump piston 84 isslidably mounted on the lower portion of the shaft. When the shaft movesdown, the piston 84 is free to slide up against shoulder 94 whereby head92 is removed from seat and fluid chemical from the space below thepiston is free to flow through the check valve 90, 92 to the space abovethe head. A ball check 96 at the bot tom of cylinder 72 preventschemical from flowing out the bottom of the cylinder.

Downward movement of motor drive piston 42 forces shaft 70 down wherebypump piston 84 is forced through the liquid in the pump cylinder untilhead 92 comes to a rest on ball check 96 thus preventing further fluidflow. On the return stroke piston 42 and shaft 70 move upwardly. Head 92is drawn into engagement with seat 90 and piston 84 is pushed up. As thepiston 84 moves up it creates a suction which draws a new supply ofchemical through check valve 96. Acting like a pump piston on its upstroke, piston 84 forces the liquid above it into outlet conduit 36until shoulder 76 on the upper end of piston 84 seats against shoulder82 thus preventing further fluid flow.

To initiate that cycle of operation of chemical flushing and pumping,the control valve shaft 66 is released. Spring 68 returns it to upposition. Gas pressure is then applied to the bottom of piston 42 andboth pistons move up. They move up until piston 84 reaches stop 82.Meanwhile the chemical above the piston is forced out of the pumpcylinder and more is drawn in below the piston.

Whilethe valve shaft 66 is up and the pistons are up, or are moving up,pressure is being applied by line 32 to one of the flushing valve motors24 or 25. Since the pumping stroke is only a few seconds long andflushing is desired for one or more minutes, the apparatus fordepressing shaft 66 is arranged to provide that timing. After a shorttime, long enough for the piston 42 to have reached bottom position,control valve shaft 66 is depressed, pistons 42 and 84 move down andchemical fills the space above piston 84.

In the embodiment shown in the drawings, the timer 100 and a battery 102are mounted on a plate I04 which is fixed to the top of cylinder 40. Thetimer controls a motor 105 whose shaft 106 is visible in FIG. 2. A cam108 is carried on that shaft. When the motor is energized, the camrotates slowly. In one example it revolves once in 2 minutes. The cam108 has a projection on its periphery which, over about of cam rotation,acts to depress a lever 110 about its pivot 112. That lever engagesshaft 66 ofcontrol valve 44 and depresses shaft 66 for 4 or 5 seconds ofeach 2-minute interval. That ratio of flushing time to pumping time canbe changed by changing cams. V I

In this embodiment the lever 110 is spring biased to its upper positionby the spring 68 that is seen "in FIG. 3 to be contained within thevalve 44. In an alternative arrangement the cam is provided with acontinuous track. A follower that moves in that track is fixed to thevalve operator 66. Whatever the construction, motion of the valve stem66 or the cam 108 or the lever 110 also controls the actuator of aswitch 114. That switch is normally closed and is opened only when, asillustrated schematically in FIG. 4, the projection on cam 108 acts todepress the lever 110 and the operator 66 of control valve 44.

Switch 114 forms part of the timer 100. A preferred form of that timeris shown in FIG. 4, it being understood that the battery 102 isconnected across the terminals marked and of FIG. 4. A clock oscillator140, which may comprise a unijunction oscillator, furnishes pulses at agiven pulse rate to a divider 142. The divider may have conventionalform and may in fact comprise an integrated circuit-type CD402OE.Division is accomplished by stages and output signals at differentfrequencies are available at each of those stages. In the embodimentshown in FIG. 4, 10 output signals are available. Those signals have theform of pulses that are separated by different intervals. The fiveterminals that extend to the right in FIG. 4 furnish pulses after longintervals. The intervals in this case are representative and are onehalf-day, 1 day, 2 days, 4 days, and 8 days, respectively. Pulsesseparated by very much shorter intervals are available at the fiveterminals that extend downwardly from the divider in FIG. 4. In thiscase intervals of l 1 minutes, 23 minutes, 45 minutes, 90 minutes and l80 minutes are available. One of the five ter minals at the right isconnected by a switch 144 to the base of a transistor 146 throughcapacitor 145. One of the five terminals at the bottom of the divider isconnected by a switch 148 to the base of a transistor 150. The emitterof transistor 146 is connected to the positive line 152. The collectorof that transistor is connected through a resistor 154 to the negativeline 156. The DC motor 105 is connected from line 152 to line 156 inseries with a silicon controlled rectifier 160 whose control electrodeis connected to the junction between resistor I54 and the collector oftransistor 146. Switch 114 and the emitter-collector circuit oftransistor 150 are connected in series in parallel with the siliconcontrol rcctificr 160.

The silicon controlled rectifier SCRI60 is turned on by a signal appliedto its control electrode as a result of the application of a signal tothe base of transistor 146 from one of the long interval outputterminals of the divider. The rectifier continues conducting until thevoltage drop across it is lowered to near zero. The voltage drop will belowered and conduction will stop when the parallel circuit throughswitch 114 and transistor 150 is complete to short circuit the SCRI60.The motor will rotate when the SCR is conducting. Itwill continue torotate through a small angle after the SCR is shorted because a currentpath is maintained through switch 114 and transistor 150. The shortcircuit is completed only when switch 114 is closed. The short isterminated when the motor rotates the cam enough to permit opening. ofthe switch. In view ofv that the at rest condition isone in which themotor has moved lever to a position in which switch 114 is open and thevalveoperator 66 is depressed. Thus the condition that valve44 is shownto have in FIG. 2 is the at rest condition.

If it is assumed that switch 114 is connected to the 8-day divideroutput terminal and that the switch 148 is connected to the 90-minutedivider output'and that the cam 108 revolves once in 2 minutes, then thetiming system will operate as follows.

At the end of an 8-day interval a signal will be applied through switch144 and transistor 146 to trigger the SCR. That will complete thecircuit from battery 102 through the motor and the SCR. The motor willrotate until the SCR is turned off. During each revolution of the cam108, the switch 1 14 will close for a few seconds but that will notserve to complete the short circuit until 90 minutes have elapsed.

All outputs of the divider are derived from the same input pulse so alloutput signals are coherent. The 90 minute interval begins when the8-day interval ends. Thus the transistor 150 will be turned off for 90minutes while the cam 108 rotates 45 times. At the end of 90 minutestransistor 150 is turned on. The SCR will be shorted when cam 108 nextcloses switch 114. Rotation continues because of current through theshort until the switch opens. A turn on signal will be applied to thebase of transistor 150 every 90 minutes but the transistor does not turnon because the circuit is open at switch 114. Thus the system remains atrest until the SCR is retriggered at the end of 8 days.

When each of the 45 revolutions of cam 108 during the 90 minute on time,the operator 66 of valve 44 is released and depressed. The chemical pumpoperates 45 times and each of those 45 times motor 24, or motor 25,operates the valves that flush the chemical down the well.

In this embodiment there are two motors coupled to shaft 106. One is asmall gas turbine 220 which is driven by gas from line 26 when valve 222is opened by solenoid 224. The other is the electric motor 105. A singlepole double throw switch 228 selects either the motor of the solenoidfor connection to the DC. power source. If gas pressure is high the gasmotor would be selected to preserve battery power.

Returning to FIG. 2, the area of piston 42 is many times greater thanthat of piston 84. Nearly six times greater in this embodiment. Thestroke of the two pistons is almost the same, differing only to theextent that piston 84 can move relative to shaft 70. Thus, chemical isdelivered to the well casing, in this particular embodiment, at apressure above atmospheric pressure approximately six times the wellproduct pressure. An adequate quantity of chemical is introduced intothe well at each treatment by adjusting timer 116 so that the pump willbe operated for an adequate number of cycles.

I claim:

1. Apparatus for use in applying chemical from a storage container tothe casing of a well of the kind in which fluid product issues atpositive pressure from a tubing string in the casing comprising:

a gas separator for connection to said tubing string such thatpressurized gas is separated from said product and stored;

a pumping means including a pump and flow conduits for transferringchemical from said storage container to said well casing and a gaspressure powered driver for driving said pump, the driver havingmechanical advantage over the pump such that delivery pressure from thepump exceeds the pressure applied to the driver;

a normally closed, pressure-opened connection from the tubing to thecasing of the well;

a line connecting the separator to said driver and to saidpressure-opened connection;

control means including valving in said line and a timer for actuatingsaid valving for causing the driver to operate the pump and for openingsaid connection a predetermined number of times after a predeterminedinterval;

said pumping means comprising a driver cylinder and LII piston and apumping cylinder and piston, the two pistons being mounted on a commonshaft for reciprocation together in their respective cylinders and thepump piston and cylinder having smaller crosssectional area than thedriver piston and cylinder;

said control means comprising a three-way valve having an inlet forconnection to said gas separator and having two alternate outlets eachconnected to the driver cylinder at a respectively associated side ofthe driver piston, one of the outlets of said three-way valve beingconnected to said pressure-opened connection;

means for mounting said pumping means such that it can extend throughthe bung hole of a drum with its pump extending within the drum; and

said three-way valve including an operating shaft and in which saidtimer comprises a rotating cam position to actuate said cam in a givenrotational position and means for rotating said cam for a given periodduring a longer period.

1. Apparatus for use in applying chemical from a storage container tothe casing of a well of the kind in which fluid product issues atpositive pressure from a tubing string in the casing comprising: a gasseparator for connection to said tubing string such that pressurized gasis separated from said product and stored; a pumping means including apump and flow conduits for transferring chemical from said storagecontainer to said well casing and a gas pressure powered driver fordriving said pump, the driver having mechanical advantage over the pumpsuch that delivery pressure from the pump exceeds the pressure appliedto the driver; a normally closed, pressure-opened connection from thetubing to the casing of the well; a line connecting the separator tosaid driver and to said pressure-opened connection; control meansincluding valving in said line aNd a timer for actuating said valvingfor causing the driver to operate the pump and for opening saidconnection a predetermined number of times after a predeterminedinterval; said pumping means comprising a driver cylinder and piston anda pumping cylinder and piston, the two pistons being mounted on a commonshaft for reciprocation together in their respective cylinders and thepump piston and cylinder having smaller crosssectional area than thedriver piston and cylinder; said control means comprising a three-wayvalve having an inlet for connection to said gas separator and havingtwo alternate outlets each connected to the driver cylinder at arespectively associated side of the driver piston, one of the outlets ofsaid three-way valve being connected to said pressure-opened connection;means for mounting said pumping means such that it can extend throughthe bung hole of a drum with its pump extending within the drum; andsaid three-way valve including an operating shaft and in which saidtimer comprises a rotating cam position to actuate said cam in a givenrotational position and means for rotating said cam for a given periodduring a longer period.